Numerous treatment modalities for tinnitus have been attempted, including drugs, noise-masking, Tinnitus Retraining Therapy, Neuromonics, and electrical stimulation. Cochlear electrical stimulation (CES) via cochlear implants is a frequently studied approach due to its promising results in managing patients' tinnitus. Cochlear implants and their speech processors are mainly designed for hearing restoration, however, CES has not been specifically designed and used to manage tinnitus. In addition, the underlying mechanisms of CES-induced tinnitus suppression remain unclear. In this project, we propose to develop a rat model of CES-induced tinnitus suppression using new thin-film based cochlear implant devices and to investigate the underlying neural mechanisms of the induced tinnitus suppression. Specifically, in Aim 1, we will test whether CES suppresses behavioral evidence of tinnitus in rats and whether CES induces more robust tinnitus suppression than auditory cortex or cochlear nucleus stimulation. In addition, we will test different parameters such as stimulation locations (apical vs. basal stimulation), patterns (single pulse vs. pulse train stimulation), duration, rate and intensity in order to identify optimal stimulation strategies. In Aim 2, we will elucidate the underlying mechanisms of CES-induced tinnitus suppression by investigating its induced changes in neural correlates of tinnitus in the rat auditory cortex. Specifically, we will determin whether CES-induced tinnitus suppression results from down-regulation of tinnitus-related hyperactivity, neurosynchrony, bursting, and tonotopic reorganization in the auditory cortex. Developing this animal model will enable extensive testing of stimulation parameters to identify optimal strategies for tinnitus suppression, and will determine whether peripheral modulation is more effective than central modulation and whether bottom-up modulation is more robust than top-down modulation. Elucidation of the mechanisms underlying CES-induced tinnitus suppression will provide information to help improve clinical trials and tinnitus management. Our novel thin-film-based cochlear implants will help us to develop new and effective devices optimized for tinnitus suppression.